This invention relates to an automatic electronic flash device sometimes called a computer flash device and particularly relates to a flash device to improve visibility of the signal lamps conventionally associated with the device.
Known flash devices of this type are provided with two signal lamps at the rear of the flash device. On the other hand, the housing containing the light sensitive sensor sometimes called the external sensor, is attached to the view finder connector shoe of the camera in such a manner that the sensor is directed in the direction of the object to be photographed.
One of the signal lamps is connected to the flash capacitor to indicate to the photographer whether or not the flash capacitor has been charged to a sufficiently high voltage so that a flash exposure is possible. As is well known, the external sensor disposed at the camera receives the flash light reflected from the object and compares the measured light intensity with a value corresponding to the optimum illumination. When this value has been reached, the automatic arrangement of the flash device interrupts the discharge of the flash lamp to be extinguished. This enables the photographer to determine whether the automatic arrangement is active or whether the distance to the object to be photographed is too large and therefore a sufficiently exposed film cannot be obtained (which can generally be recognized in that the automatic circuit does not respond). The second signal lamp lights up as soon as the flash lamp has, in fact, been automatically extinguished.
In such flash devices having an external sensor it is conventional practice to connect the flash device with a camera by means of rail or it is held by hand or is disposed at some convenient place in the room. Upon arranging the two signal lamps at the rear surface of the flash device the photographer who wants to assure himself whether the flash device is ready to function or whether the flash light automatic arrangement has functioned, is forced to move his eye before and after each exposure from the viewfinder of the camera to check whether the signal lamps of the flash device are illuminated. This is not only disagreeable, but valuable opportunities for taking pictures may be missed.
In a known flash device which is connected with the photographic camera and which is only provided with a single signal lamp to indicate that the flash lamp is ready, this disadvantage is removed in the following manner. An indicator element is disposed in the optical path of the viewfinder of the camera, the indicator element being, for example, a luminescent diode or the like which can be connected to the output of a circuit, the input signal of which is derived from the feed current of the flash lamp. The photographer then recognizes when he looks through the viewfinder whether the flash device is ready to function or not.
The disadvantage of this construction is that it requires a special design of the flash device and camera. Accordingly, such flash devices and cameras cannot be utilized separately with other flash devices or cameras. Furthermore, the introduction of two signal lamps in the optical path of the viewfinder of the camera in somewhat questionable particularly if the camera is already "loaded" with sophisticated technical equipment because frequently in that case, the viewfinder is already filled with various indicator elements for time and aperture values.